Thursday, May 1, 2014

New paper finds large erroneous assumption about natural land sinks for CO2

A new paper published in Global Change Biology finds another large erroneous assumption of the carbon cycle, finding the natural land carbon sink in India is 42% less than previously believed. This implies that the net natural contribution of CO2 and other "CO2 equivalents" such as methane to the atmosphere could be significantly larger than previously believed.

According to the authors, large amounts of carbon dioxide equivalents taken up by plants on land are returned to the atmosphere from aquatic environments, finding "average inland water greenhouse gas emissions, which were not previously considered, correspond to 42% of the estimated land carbon sink of India. Thereby this study illustrates the importance of considering inland water greenhouse gas exchange in large scale assessments."

This 42% carbon sink error, huge in comparison to the 4% of total CO2 emissions generated by burning of fossil fuels, is just one of many recent published papers demonstrating how little is actually known about the global carbon cycle and natural sinks/sources of CO2, which are more than an order of magnitude larger than the man-made sinks/sources of CO2. Thus, the IPCC Bern model of the carbon cycle, which is based upon older, highly erroneous assumptions obviously cannot be relied upon to predict future greenhouse gas concentrations. Climate models in turn use the erroneous output of the Bern model to create the science fiction greenhouse apocalypse projections for the future.

Large amounts of carbon dioxide equivalents taken up by plants on land are returned to the atmosphere from aquatic environments. This according to a study carried out by two master's students at Linköping University.

Emissions of carbon dioxide equivalents – such as methane and carbon dioxide – from lakes, ponds, rivers, open wells, reservoirs, springs, and canals correspond to on an average 42% of the expected natural carbon sink in India.

These are the findings of the study by master's students Bala Panneer Selvam and Sivakiruthika Natchimuthu, students at the Science for Sustainable Development master's programme. They have done a thorough investigation of greenhouse gas emissions from many types of inland waters in India under supervision of Dr Lakshmanan Arunachalam, Tamil Nadu Agricultural University, India, and Dr David Bastviken, Linköping University, Sweden.

"This carbon sink may therefore be smaller than expected, illustrating that we do not have full knowledge of the natural greenhouse gas balance," says Dr Bastviken. "Hence, it may be better to try to reduce fossil carbon emissions rather than hoping that natural environments have a large capacity to take up emitted carbon."

Methane accounted for 71% of the emitted aquatic CO2 equivalents and this opens up possibilities to reduce these emissions by reducing the water pollution in terms of nutrients and organic material.

"It is important to point out that these findings are not specific for India – all countries should consider aquatic emissions in their greenhouse gas balances."

The study also illustrates how student projects can contribute to science that attracts global interest. It was recently published in the scientific journal Global Change Biology, with the title Methane and carbon dioxide emissions from inland waters in India – Implications for large scale greenhouse gas balances.

Inland waters were recently recognized to be important sources of methane (CH4) and carbon dioxide (CO2) to the atmosphere, and including inland water emissions in large scale greenhouse gas (GHG) budgets may potentially offset the estimated carbon sink in many areas. However, the lack of GHG flux measurements and well-defined inland water areas for extrapolation, make the magnitude of the potential offset unclear. This study presents coordinated flux measurements of CH4and CO2 in multiple lakes, ponds, rivers, open wells, reservoirs, springs, and canals in India. All these inland water types, representative of common aquatic ecosystems in India, emitted substantial amounts of CH4 and a major fraction also emittedCO2. The total CH4 flux (including ebullition and diffusion) from all the 45 systems ranged from 0.01 to 52.1 mmol m−2 d−1, with a mean of 7.8 ± 12.7 (mean ± 1 SD) mmol m−2 d−1. The mean surface water CH4 concentration was 3.8 ± 14.5 μm (range 0.03–92.1 μm). The CO2 fluxes ranged from −28.2 to 262.4 mmol m−2 d−1 and the mean flux was 51.9 ± 71.1 mmol m−2 d−1. The mean partial pressure of CO2 was 2927 ± 3269 μatm (range: 400–11 467 μatm). Conservative extrapolation to whole India, considering the specific area of the different water types studied, yielded average emissions of 2.1 Tg CH4 yr−1 and 22.0 TgCO2 yr−1 from India's inland waters. When expressed as CO2 equivalents, this amounts to 75 Tg CO2 equivalents yr−1 (53–98 Tg CO2 equivalents yr−1; ± 1 SD), with CH4 contributing 71%. Hence, average inland water GHG emissions, which were not previously considered, correspond to 42% (30–55%) of the estimated land carbon sink of India. Thereby this study illustrates the importance of considering inland water GHG exchange in large scale assessments.